JPS6348629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a DC arc welding material and an arc welding machine with improved arc stability of a DC TIG welding machine.

Conventional configuration and its problems Single-phase rectifier DC arc welding machines have larger ripples in the output current than three-phase rectifier DC arc welders, so it is necessary to reduce the ripples in the output current and use a unidirectional control rectifier element. Output-adjustable DC arc welding machines with phase control have been used.

FIG. 1 shows a conventional example. 1 is a welding transformer; 2a and 2b are unidirectional control rectifier elements (hereinafter referred to as unidirectional thyristors); 3a and 3b are rectifier elements (hereinafter referred to as diodes); 4a and 4b are wound on the same iron core, and each is energized. 5 is a welding load, which is a reactor with approximately equal inductance so that the magnetic flux generated on the iron core is in the same direction.

Let the terminals of the secondary winding of the welding transformer 1 be A and B,
When terminal B is positive and terminal A is negative, when a gate signal is input to unidirectional thyristor 2b, unidirectional thyristor 2b is forward biased in the previous cycle, so it turns ON, and the current flows to terminal B, unidirectional thyristor 2b, and reactor. 4b, welding load 5, diode 3a, and terminal A. At this time, reactor 4b
In this case, a positive voltage is induced on the cathode side of the unidirectional thyristor 2b, and energy is stored. During this time, the reactor 4a reversely biases the anode side of the unidirectional thyristor 2a to negative. Next, when the voltage at terminal B decreases and there is no longer enough power to supply energy from the welding transformer 1 to the reactor 4b, energy is released from the reactor 4b, and the unidirectional thyristor 2 is connected to the reactor 4b.
The cathode of b induces a negative voltage, and the anode side of the unidirectional thyristor 2a induces a positive voltage in the reactor 4a, so that the unidirectional thyristor 2a is forward biased. In this state, when a gate signal is applied to the unidirectional thyristor 2a, it turns ON because it is forward biased, and current flows to terminal A, diode 3b, welding load 5, reactor 4a, unidirectional thyristor 2a, and terminal B. At this time, a voltage that reverse biases the unidirectional thyristor 2b is induced in the reactor 4b, so the unidirectional thyristor 2b is turned off. Similarly, commutation and smoothing are performed using energy accumulation and release from the reactor 4a, and a DC output current is obtained. However, in this method, the energy storage and release in the reactors 4a and 4b via the welding load 5 occurs only when the unidirectional thyristors 2a and 2b conduct, and the ripple rate increases as the current decreases. In order to obtain a ripple rate of about 30%, it was necessary to create an extremely large reactor. Therefore, the weight of the welding machine is heavy,
It had the disadvantage of being large.

OBJECTS OF THE INVENTION The present invention eliminates the drawbacks of the conventional examples and enables a DC arc welding machine and a DC TIG welding machine that are small, lightweight, and have excellent arc stability.

Structure of the Invention To achieve this object, the present invention provides a first unidirectionally controlled rectifying element cathode and a first rectifying element connected to each other at both ends of a secondary winding of a welding transformer whose primary winding is connected to a power source. a cathode is connected, first and second reactors are connected in series between an anode of the first unidirectionally controlled rectifying element and an anode of the first rectifying element, and a secondary winding of the welding transformer. The anode of the second unidirectionally controlled rectifying element is connected to the terminal to which the cathode of the first unidirectionally controlled rectifying element is connected in the line, while the terminal to which the cathode of the first unidirectionally controlled rectifying element is connected is connected to the second rectifying element. The anodes of the elements are connected, and a welding load is applied between the connection point between the cathode of the second unidirectional control rectification element and the cathode of the second rectification element and the connection point of the first and second reactors. and a resistor is connected in parallel to the first and second unidirectionally controlled rectifying elements, and the first and second reactors are wound on the same iron core with substantially constant inductance. The magnetic flux generated on the iron core when the second unidirectional rectifying element is alternately conductive is in the same direction. With this configuration, the ripple rate of the output current can be reduced from small currents to large currents without having to make the reactor as large as before, so it is possible to use a DC arc welder or DC TIG with extremely stable arc.
This can be achieved by making the welding machine smaller and lighter.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 2 to 4 a and b of the drawings. In FIG. 2, a welding transformer 1, unidirectional control rectifying elements (unidirectional thyristor) 2a, 2b, rectifying elements (diodes) 3a, 3b, reactor 4a, and welding load 5 are the same as those in the conventional example shown in FIG. In this example, the first
In the configuration shown in the figure, the position of the reactor 4b' is changed and the resistors 6a and 6b are replaced by the unidirectional thyristors 2a and 2.
-b are connected in parallel to each other.

To explain the operation below, when terminal B of the secondary winding of welding transformer 1 is positive and terminal A is negative,
When a gate signal is input to the unidirectional thyristor 2b, the unidirectional thyristor 2b is forward biased in the previous cycle, so it turns ON, and the current flows through terminal B, unidirectional thyristor 2b, reactor 4b', welding load 5, diode 3a, and terminal A. flows to At this time, the anode side of the diode 3a becomes negative and energy is stored in the reactor 4b'. During this time, the reactor 4a reversely biases the anode side of the unidirectional thyristor 2a to negative. Next, when the voltage at terminal B decreases and there is no longer enough power to supply energy from welding transformer I to reactor 4b',
Energy is released from reactor 4b'. At this time, the energy of the reactor 4b' is transferred to the reactor 4b', the diode 3a, the diode 3b,
The discharge is carried out via the welding load 5 to the welding load 5 and the reactor 4b'. On the other hand, the unidirectional thyristor 2a is forward biased by the induced voltage of the reactor 4a, and when the gate signal is input, it turns on and current flows to the terminal A, the diode 3b, the welding load 5, the reactor 4a, the unidirectional thyristor 2a, and the terminal B.
The same operation is repeated below. This differs from the case shown in FIG. 1 in that a circuit is formed in which the energy of the reactor 4b' is released via the welding load 5 in this way. Therefore, the energy of the reactor 4b' can be used effectively, and the ripple rate of the output current can be improved.

On the other hand, when the firing phase of the unidirectional thyristors 2a and 2-b is narrowed down, the ripple rate increases although the energy of the reactor 4b' can be used effectively. The resistors 6a and 6b reduce this, and the output current is the composite current with the single-phase full-wave output current limited by the resistors 6a and 6-b (see Figure 3a), so the ripple rate is is extremely small compared to the conventional example (see FIG. 3b). Therefore, arc stability at low currents is dramatically improved. Furthermore, this embodiment (see Fig. 4a) is different from the conventional example (see Fig. 4b).
The ripple rate of the output current is better in all regions than in the previous model.

Effects of the Invention According to the present invention, the ripple rate of the output current can be reduced in the entire current range using a reactor with a smaller inductance than the conventional one, without making the reactor as large as the conventional one. This has an excellent effect of providing a stable arc welding machine.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional arc welding machine, Fig. 2 is a circuit diagram of an arc welding machine according to an embodiment of the present invention, Fig. 3 a and b are output current waveform diagrams of this embodiment and a conventional example, FIGS. 4a and 4b are output current waveform diagrams in the same entire range. 1... Welding transformer, 2a, 2b... Unidirectional control rectifying element, 3a, 3b... Rectifying element, 4a, 4
b'...Reactor, 5...Welding load, 6a, 6b
……resistance.

Claims (1)

[Claims] 1. A cathode of a first unidirectional control rectifying element and a cathode of the first rectifying element are connected to both ends of a secondary winding of a welding transformer whose primary winding is connected to a power source, and the first unidirectional control is performed. first and second reactors are connected in series between the anode of the rectifying element and the anode of the first rectifying element, and the first unidirectionally controlled rectifying element is connected in the secondary winding of the welding transformer The anode of a second unidirectionally controlled rectifying element is connected to the terminal to which the cathode is connected, while the anode of the second rectifying element is connected to the terminal to which the cathode of the first rectifying element is connected, and A welding load is connected between a connection point between a cathode of the unidirectional control rectifying element and a cathode of the second rectifying element and a connection point of the first and second reactors, and
A resistor is connected in parallel to the unidirectionally controlled rectifying elements, and the first and second reactors are wound on the same iron core with substantially constant inductance, and the first and second unidirectionally controlled rectifying elements are alternately connected. An arc welding machine that directs the magnetic flux generated on the iron core in the same direction when conductive.